In current mobile communication devices, such as mobile telephones, an important feature is that of being able to communicate in different communication networks. That is, the hardware and software of the devices need to support multiple radio access technologies, such as the third generation partnership project, 3GPP, Global System for Mobile Communications, GSM, Wideband Code Division Multiple Access, WCDMA, Long Term Evolution, LTE and the Chinese Time Division Synchronous Code Division Multiple Access, TD-SCDMA, systems. A consequence of this is that neighbor cell measurements have to be done across all the supported radio access technologies. Neighbor cell measurement is a procedure that takes place when a mobile communication device is camped on a cell (i.e. in connection with a radio base station that maintains a radio cell) using a particular radio access technology (WCDMA for instance) and is in a connected mode, it needs to create time gaps in its radio signal reception process, in order to create measurement occasions for neighbor cells (i.e. cells that are geographically adjacent or even overlapping the cell on which the mobile communication device is camped) which belong to other radio access technologies like LTE or GSM. These measurement occasions (or gaps) have to be shared (i.e. gaps created by one RAT is a common resource to be used to measure neighbor cells of all other RATs) such that measurement reporting deadlines are met for all the cells in the neighbor cell list of the mobile.
When a mobile is camped on a WCDMA cell, then the measurement gaps are created and published (i.e. made available for sharing) by controlling entities in the network with a specific purpose. For example, a gap needs to be used for GSM received signal strength indicator, RSSI, measurements or base station identity code, BSIC, Identification or BSIC Reconfirmation). In such a situation, the mobile communication device has to just use the measurement gaps with the purpose specified by the network and it is expected that measurement reporting deadlines will be met. But, when the mobile is camped on an LTE cell, the measurement gaps are published without any specific purpose. So the mobile phone needs to implement logic to effectively use the published gaps such that all its measurement deadlines are met.
Moreover, LTE also has a discontinuous reception, DRX, and a non DRX mode of operation for saving power drained from the power source of the device. The deadline for sending the periodic measurement reports to the LTE network is different for the two modes. The mobile communication device can alternate between the DRX and non DRX modes very dynamically and, as a consequence of this, the deadline becomes ambiguous. Furthermore, GSM being a time division multiple access, TDMA, based system, the measurements like BSIC reconfirmations have to be done at specific instances and a measurement gap at any instance is therefore not useful. For BSIC identification the timing of the cell is unknown and a continuous time of 97 GSM slots (or 57 milliseconds) is needed for a guaranteed detection of a signal that carries the BSIC. But since measurement gaps published by LTE cells are much shorter duration (in fact the duration of the LTE gaps are 6 milliseconds) the detection becomes unpredictable.